The present invention relates to a gear mechanism for a vehicle seat adjuster.
An open planetary gear train (D gearing) may be used as a drive for an adjuster of a vehicle seat, wherein an inactive gearing acts as a locking device. Manufacturing-related tolerances of the components may lead to a backlash at the driven end. In the case of a locked gearing, this backlash may cause noises and undesired movements in the driving operation. On the other hand, the actuation of the gearing requires a minimum backlash of teeth, for obtaining a uniform adjustment. In a gear mechanism disclosed in DE 195 27 374 C2, which is designed and constructed as a simple reversing gear mechanism with an upper member as a center gear and a lower member as a planet gear, a wedge sliding device is proposed. An axial displacement of a slide permits eliminating a radial backlash between the two members of the mechanism. However, this solution cannot be transferred to a gear mechanism of the initially described kind, which is used for cases without a wobbling motion, since the increased number of components between a plurality of components does not permit eliminating the backlash at the same time.
It is therefore an object of the present invention to improve a gear mechanism of the initially described kind.
The above and other objects and advantages of the present invention are achieved by the provision of a gear mechanism which comprises at least two hollow wheels having internal gears and being mounted in a side by side arrangement for relative rotation, at least one rotatable planet gear positioned to selectively engage the internal gears of the two hollow wheels, and means acting in radially different directions for eliminating play between the internal gears of the two hollow wheels. Preferably the means for eliminating play operates in radially opposite directions on the planet gear and one of the hollow wheels, respectively.
As a result of providing means acting in radially different directions, which eliminate a radial backlash in the locked state of the gear mechanism, it is possible to realize a zero backlash likewise in a gear mechanism with more than two components that are adapted for rotation relative to one another. For example, in the case of three components that are capable of rotating relative to one another, it is possible to eliminate with these means, which operate preferably in radially opposite directions, the radial backlash between the planet gear and respectively one of the two hollow wheels at the same time. Preferably, the radially different action is achieved by an axial movement of the means, for example, by means of a tie rod. Such a simplified construction makes it possible to better act upon means provided in the interior of the gear mechanism, without adversely affecting their pivoting function.
The means may be designed and constructed as a rotary slide joint, for example, an axially displaceable bearing for the gears for purposes of being operative both in the radial and in the axial direction. Preferably, the means are provided with a wedge sliding device, which converts in the case of an activation, an axial force into a radial force and an axial displacement into a radial displacement. In a preferred construction of the means in the form of bearing sleeves, the outer wall surfaces form the rotary joint, whereas an inner guide track for a wedge forms the wedge sliding device.
To apply the force for eliminating the backlash, it is preferred to provide an energy storage, for example a spring, for purposes of moving the means. To activate or deactivate the backlash elimination selectively between a locked and an operative state of the gear mechanism, the energy storage is preferably adapted for disengagement. To this end, the drive is provided with radial cams for disengaging the energy storage.
The gear mechanism of the present invention is used preferably in a vehicle seat, in particular in an automobile seat, for example, in an inclination adjuster for the entire seat surface (bucket) or for a portion of the seat surface, for the seatback and/or the head rest, or in a height adjuster, in particular in locations, where forces occur.